A decubitus ulcer, or pressure ulcer as it is more commonly known, is a localized wound of variable depth caused by prolonged pressure in a patient allowed to lie too still in bed over an extended period of time. Sustained compression of the cutaneous and subcutaneous tissue between the bony prominences of the patient's body and the support structure, e.g. the mattress, has been cited as a primary cause of pressure ulcer formation. Thus, the sites most often affected in bed-ridden patients include the sacrum, greater trochanter, heel and scapula--these are the sites which usually experience higher pressures or loads due to body weight distribution.
From the treatment of patients in acute care facilities to their care in the home setting, the incidence of pressure ulcer development, and the degeneration of tissues associated with such ulcers, once formed, present a significant health care problem both in terms of the amount of financial resources expended in treatment and, more importantly, in the morbidity and mortality associated with the complications which often arise. Depending on the severity of the pressure ulcer and the medical condition of the patient, it has been estimated that the cost of treatment can be as high as $40,000 (Brandeis et.al., JAMA 264:2905-2908 (1990)). In one study it was reported that the rate of occurrence of bacteremia associated with pressure ulcers was 3.5 events per 10,000 hospital discharges. The hospital mortality rate from this complication alone was estimated to be 50% (Allman, Decubitis 2:30-33 (1989)).
Although current understanding of pressure ulcer etiology is incomplete, it is known that the development of such ulcers is the result of a myriad of factors which often interact with one another in a complex manner. It has been recognized that purely conservative measures can be used to control one or more of these factors and that these measures alone can result in the prevention of pressure ulcer development and in more effective treatment of those which have developed. One conservative measure which has been identified to be of critical importance in this regard, is the choice of effective support surfaces, such as wheelchair cushions as well as other seating devices and, more importantly, mattresses, which are utilized in the day-to-day patient care. In the following discussion, the general term "support structure" will encompass such varied products as beds, mattresses, cushions, mattress overlays and covers, and sheets, in addition to operating room tables and other types transitional structures i.e, all types of products with which a patient might have contact.
All of the products mentioned above impinge upon defined areas of a patient's body and so present their own unique set of problems and concerns for healthcare workers and researchers in the field of pressure ulcer prevention. For example, the areas at risk of pressure ulcer development as a result of inadequately designed seating devices center primarily around the ischium but can involve the posterior regions of the knee joints and lower thigh. More generalized areas are at risk of pressure ulcer development however, when the design of operating room tables and other transitional structures is examined.